1. Field of the Invention
The invention relates to a displacement machine for compressible mediums with at least one spiral-shaped conveying space, which is disposed in a stationary housing and which spans a circumferential angle of approximately 360.degree.. A spiral-shaped member is assigned to this conveying space, spans a circumferential angle of approximately 360.degree. and is held in such a manner on a disk-shaped rotor, driven off-centered with respect to the housing, that during service each of its points effects a circular movement defined by the circumferential walls of the conveying space, and its curvature with respect to that of the conveying space is dimensioned in such a manner that it almost touches the inner and outer circumferential walls of the conveying space at at least one sealing line that advances continuously during operation.
2. Background of the Invention
Displacement machines of the spiral design are known, for example, from DE-C-26 03 462. A compressor built according to this principle provides an almost pulsation free conveying of the gaseous working medium, which consists of, for example, air or a mixture of air and fuel. It could also be used advantageously for the purpose of charging internal combustion engines. While such a compressor is operating, several possibly crescent-shaped working spaces, which move from the inlet through the displacement chamber to the outlet, are enveloped along the displacement chamber between the spiral-shaped displacement body and the two circumferential walls of the displacement chamber, thus resulting in their volume being continuously decreased and the pressure of the working medium being increased correspondingly. In this machine one proceeds on the assumption that the circumferential angle of the spirals leads to a compressor with internal compression. To this end, a second spiral element having a significantly shorter radius of curvature is attached to produce a spiral extending over 360.degree..
A machine of the aforementioned kind, in which the spirals span a total circumferential angle of approximately 360.degree., is known from the EP-A-0 321 781. In these machines, which are used to charge internal combustion engines, it has been demonstrated that a geometrically internal compression of approximately 1 is the optimal value. Thus, the aforementioned second spiral element having a significantly smaller radius of curvature can be dispensed with. These known machines work with a displacement body whose spiral walls are attached on both sides to a central wall. The radially inner region of this central wall exhibits passage openings which enable the air conveyed by the drive-sided part of the spirals to flow into the air-sided section, in order to be withdrawn from the machine. On each side of the central wall there are two telescoped spirals, whose exits are offset by 180.degree.. The conveying spaces arranged in the housing are configured correspondingly. The result is that the clear diameter between the inner walls of the conveying space at the spiral exit is pertinent for the available space. In this available space, however, must be accommodated not only the working medium displaced by the orbiting spirals, but also the drive shaft with the eccentric and the compensating weights.